1. Industrial Application Field
The present invention relates to prevention of illegal copies of disc-like optical recording media and prevention of illegal install of information into information processing systems or the like, and more particularly to a method and system for preventing recorded music on optical disks, as well as projected images and various sorts of programs, such as game softwares (softs) and computer softwares, from being illegally copied and utilized without permission of the copyrighters, and further relates to an optical recording medium incapable of copy.
2. Description of the Prior Art
In recent years, optical disks are widely being employed in a variety of fields. The optical disks are generally classified into record-possible RAM disks and record-impossible ROM disks, while the manufacturing cost of the RAM disks is from five times to ten times that of the ROM disks. Accordingly, the ROM disks tend to be chiefly used in applications that supply a large number of people with a large quantity of information, for example, an electronic publication application and a medium cost-limited application that supplies music softwares and projected image softwares. On the other hand, as obvious from CD-ROM game machines and CD-ROM contained personal computers, there is a need for a RAM function being incorporated into the ROM disks, as an extension is more being made to interactive use. Home-use systems seldom require a large RAM capacity, for which reason great interest is focused on the advent of a new medium concept capable of realizing the three conditions: a small capacity RAM function, a large capacity ROM function, and a low cost. In addition, illegal duplicates of ROM disks such as CDs are recently put in the market so that the copyrighters suffer serious damage. Thus, a countermeasure has been needed for the duplicate prevention. Moreover, a soft distribution method has come into wide spread use where a plurality of encrypted (enciphered) programs are incorporated into disks and decrypted (deciphered) through passwords, and for improving the security of the password there is a need for a different ID number being recorded in each ROM.
One possible way to realize this concept is that one magnetic recording layer is equipped on the rear surface of a ROM disk, in which case the formation cost of the recording layer is less than one-tenth that of the ROM disk itself, thus realizing a partial RAM disk without greatly raising the cost of the ROM disk. Actually, as disclosed in Japanese Patent Laid-Open Nos. 56-163536, 57-6446, 57-212642, 2-179951, in terms of ROM disks such as CD-ROM not having a cartridge, there have already been proposed approaches wherein an optical recording section is provided on a front surface of a CD-ROM and a magnetic recording section is added on the rear surface thereof. In addition, Japanese Patent Laid-Open No. 60-70543 discloses an attempt to accomplish magnetic recording by means of a combination of a disk wherein, like optical disks of amorphous material, an optical recording section, made of a nonmagnetic material, is placed on its surface and a magnetic recording layer is located on its rear surface and a magnetic head which is equipped in a mechanical section facing the rear surface.
On the other hand, for the duplicate prevention, only means is known which is made to manufacture a special disk through a special process, such as intentionally making a cut or openwork on the disk, so that difficulty is encountered to manufacture it without a special manufacturing apparatus.
However, the aforesaid methods are merely based on a combination of a magnetic recording section and an optical recording section, while not containing the important requirements for definite realization of the equipment at all, such as the ways of avoiding the mutual interference between the optical recording section and magnetic recording section, permitting access to magnetic tracks with a simple arrangement, sharing a circuit, protecting magnetically recorded information on media from the external environment including magnetism and abrasion without the use of a cartridge, compressing information to be recorded in a RAM area, accelerating the access, and concretely making out a physical track format.
Furthermore, in the prior art examples, disclosure is hardly made in terms of the ways of realizing a home-use partial RAM disk in a concrete form, such as the method of mass-producing media at a low cost, which is important in realization of the media, and the method of making the media conformable with the CD standards. Therefore, there remains a problem which arises with the conventional examples in that difficulty is experienced in concrete realization of media and systems capable of home use.